In my Hive, Queen and Country Universe aliens have harvested humans 25,000 and 12,000 years ago and modified them for two sets of purposes. One is to be their general servants to aid in terraforming Mars. The second group will be simple farmers on a very different Venus, where they will grow organisms under direction of the first group.

The first group gets a full suite of genetic modifications. This includes removal of known genetic diseases. Since they will be living on Mars, which has less sunlight the first group is engineered so they can produce Vitamin D internally. What else should they have engineered into them? The aliens are only able to work in 1/2 G or less so humanity already seems physically strong and durable (human being scan survive things that will already kill most other quadrupeds (thing how fragile a horse is compared to a person). The stamina of human beings is far and away greater than most other land animals.

The immune system can be boosted. Since this is a servant relationship humans don't have to be made any smarter.

The second group is selected to be very fair skinned so they can deal with the world under the clouds of Venus. They still need Vitamin D dietary supplements, but their fair skin allows them processes the local equivalent of cod liver oil easily. I figure they will get an immune system boost as well.